Endotoxemia is associated with the appearance of tumor necrosis factor in the circulation. To assess the role of tumor necrosis factor in the systemic inflammatory responses induced by endotoxin, healthy humans will be intravenously injected with endotoxin with or without a 30-minute intravenous infusion of a recombinant tumor necrosis factor receptor-IgG fusion protein, which is known to neutralize tumor necrosis factor activity.